Anantha N V, Azam M, Sheardy R D
Department of Chemistry, Seton Hall University, South Orange, New Jersey 07079, USA.
Biochemistry. 1998 Mar 3;37(9):2709-14. doi: 10.1021/bi973009v.
We have recently reported the cation-induced self-assembly of DNA oligomers of the general sequence C4T4G4T1-4G4 into high-molecular weight multistranded structures [Marotta, S.P., Tamburri, P.A., and Sheardy, R.D. (1996) Biochemistry 35, 10484-10492]. The architecture of the proposed structure consists of a series of four leafed G4 tetrads tethered together via one or two T1-4 strands and thus resembles a long four-sided hollow tube with periodic "pockets". These pockets possess electrostatic, hydrogen bonding, and hydrophobic contact points and should be ideal candidates for the binding of small molecules. To assess the potential of using porphyrins as probes for these structures, we have investigated the interaction of tetrakis(4-N-methylpyridyl)porphine (H2TMPyP) with the simple quadruplex formed by T4G4 and with the duplex formed by CGCGATATCGCG. Visible absorption, circular dichroism, and fluorescent energy transfer studies indicate that H2TMPyP binds to both the duplex and quadruplex via intercalation at low [porphyrin]/[DNA molecule] ratios, i.e., in the presence of excess potential DNA binding sites. Analyses of Scatchard plots show that H2TMpyP binds with high affinity to both DNA secondary structures but binds to the quadruplex with an affinity 2 times greater than that of the duplex.
我们最近报道了阳离子诱导的一般序列为C4T4G4T1 - 4G4的DNA寡聚物自组装形成高分子量多链结构[Marotta, S.P., Tamburri, P.A., and Sheardy, R.D. (1996) Biochemistry 35, 10484 - 10492]。所提出结构的架构由一系列通过一条或两条T1 - 4链连接在一起的四叶G4四联体组成，因此类似于一个带有周期性“口袋”的长四边形空心管。这些口袋具有静电、氢键和疏水接触点，应该是小分子结合的理想候选者。为了评估使用卟啉作为这些结构探针的潜力，我们研究了四（4 - N - 甲基吡啶基）卟啉（H2TMPyP）与由T4G4形成的简单四重链结构以及由CGCGATATCGCG形成的双链体之间的相互作用。可见吸收、圆二色性和荧光能量转移研究表明，在低[卟啉]/[DNA分子]比率下，即存在过量潜在DNA结合位点时，H2TMPyP通过插入作用与双链体和四重链结构都结合。Scatchard图分析表明，H2TMpyP与两种DNA二级结构都具有高亲和力，但与四重链结构的亲和力比对双链体的亲和力大2倍。
